1. Technical Field
The present invention relates to the mixers of the so-called rotor-stator type, and more specifically to the mixer that includes a stator having a plurality of openings (holes) and a rotor that is disposed on the inner side of the stator and spaced by a particular gap away from the stator.
2. Description of the Prior Art
As shown in FIG. 1, it is general that the mixer of the so-called rotor-stator type comprises a mixer unit 4 that includes a stator 2 having a plurality of openings (holes) 1 and a rotor 3 disposed on the inner side of the stator 2 and spaced by a particular gap δ from the stator 2. Such mixer of the rotor-stator type is provided for subjecting a fluid or fluid or liquid being processed to the emulsification, dispersion, particle size breakup, mixing or any other similar process, by taking advantage of the fact that a high shear stress may be produced in the neighborhood of the gap between the stator 3 capable of rotating at high-speeds and the stator 2 being fixed in position. This mixer is used for mixing or preparing the fluid or fluid or liquid being processed, and has a wide variety of applications in which the foods, pharmaceutical medicines, chemical products and the like can be manufactured.
The mixers of the rotor-stator type may be classed according to the type of the circulation mode for the fluid or liquid being processed, that is, one type being the externally circulated mixer in which the fluid or liquid being processed may be circulated in the direction indicated by the arrow 5a in FIG. 2, and the other type being the internally circulated mixer in which the fluid or liquid being processed may be circulated in the direction indicated by the arrow 5b in FIG. 2.
For the mixer of the rotor-stator type, many different configurations and circulation modes or systems have been proposed. For example, the Japanese patent application No. 2006-506174, which describes the rotor and stator apparatus and method for forming the particle sizes, proposes the particle size breakup apparatus and method for forming those particle sizes in which the mixer that includes the stator having a plurality of openings (holes) and the rotor disposed on the inner side of the stator and spaced by a particular gap away from the stator can be used widely in the manufacturing fields, such as the pharmaceutical medicines, nutrition supplement foods, other foods, chemical products, cosmetics and the like. Using the apparatus and method described above, the mixers can be scaled up in the efficient, simple and easy manners.
In addition, for those past years, several indices (theories) have been reported as the performance estimation method for the mixers having the different configurations.
When the liquid-to-liquid operation is considered not only for the mixer of the rotor-stator type as described above but also for all other type mixers, for example, there are several reports in which the resulting drop diameter sizes can be discussed in terms of the magnitude (smallness or greatness) of the values that can be obtained by calculating the average energy dissipation rate (publications 1 and 2). In those publications 1 and 2, however, the method for calculating the average energy dissipation rates is not disclosed specifically.
The publications 3 to 6 report several study cases that may be applied to each individual mixer and in which the results obtained by the respective experiments have been arranged or organized systematically into the graphical chart. In those study cases (Publications 3 to 6), however, it is considered that the mixer's particle size breakup effect is only affected by the gap between the rotor and stator and by the openings (holes) on the stator. It is only described that this information differs for each different type mixer.
Several study cases are also reported (Publications 7 and 8), in which the particle size breakup mechanism for the mixer of the rotor-stator type was considered and discussed. In those publications 7 and 8, it is suggested that the energy dissipation rate of the turbulent flow will contribute to the particle size breakup effect, and the particle size breakup effect may be affected by the frequency (shear frequency) of the turbulent flow with which the particle size breakup effect is placed under the shear stress of the fluid or liquid being processed.
For the scale-up method for the mixer of the rotor-stator type, there are several reports (Publication 9) in which the final resulting drop diameter (maximum stable diameter) can be obtained during the long-time mixer running period. This, however, is not practical in the actual production sites and is of no utility. Specifically, there are no reports regarding the study cases in which the processing (agitation and mixing) time of the mixer is the object for consideration, and those study cases are not useful enough to estimate the resulting drop diameters that can be obtained during the particular mixer running period. Although it is reported that the resulting drop diameters may be estimated by considering the mixer processing time, yet it is only reported that the phenomenon (factual action) is based on the actual measured values (experimental values). In those study cases, such phenomenon is not analyzed theoretically.
In the patent application cited above, the superiority (performance) of the particular mixer and the value range of the design on which the mixer is based are disclosed, but the theoretical grounds on which the value range of the high-performance mixer design is based are not described. The types and configurations of the high performance mixers are not described specifically.
It may be appreciated from the above description that, for those past years, several indices (theories) have been reported as the performance estimation method for the mixers having the different configurations. In most cases, however, those indices can only be applied to each of the individual mixers having the same configuration. In the actual cases, however, they cannot be applied to the mixers of the various types having the different configurations. Although there are the indices that can only be applied to those mixers in which the gap between the rotor and stator will largely affect the particle size breakup effect or there are the indices that can only be applied to those mixers in which the opening portion (hole) of the stator will affect the particle size breakup effect. The indices that can be applied to those mixers that have all possible configurations are not discussed specifically. That is, there are no indices that can be applied to the mixers having all possible configurations.
As noted above, there are almost no study cases in which the performance estimation method and scale-up method for those mixers of the rotor-stator type have been defined. There are also no study cases in which those methods can be applied to the mixers of the various types having the different configurations, and the data on the results obtained by the experiments on such study cases have not been arranged or organized systematically into the graphical chart.
For the performance estimation method and scale-up method for the mixers of the rotor-stator type according to the prior art, in most cases, the final resulting drop diameters (maximum stable drop diameters) were obtained by using the small scale device for each individual mixer and permitting the device to run for the long time period, and were then estimated. More specifically, in the prior art, there is no estimation method that can be used to estimate the resulting drop diameters that would be obtained by using the large-scale devices (actual production installation) for the mixers of the various types and permitting such large-scale devices to run during the particular time period, or there is no estimation method that can be used to estimate the particular resulting drop diameters obtained during the particular running time or the processing or agitating time required until such particular resulting drop diameters can be obtained.
Although there are indices that can only be applied to the mixer in which the size of the gap between the rotor and stator may largely affect the particle size breakup effect or emulsification effec or although there are the indices that can only be applied to the mixer in which the size or configuration of the opening (hole) of the stator may largely affect the particle size breakup effect or emulsification effect. For example, there are no comprehensive indices that can be applied to the mixers having the various configurations (the theories on which the various types of mixers can be compared or estimated comprehensively) were not discussed, and there are no indices that take the above discussion into consideration.
The performance of the mixer was actually estimated on the error and trial basis using the actual fluid or liquid being processed, therefore, and the mixers ware then designed, developed and fabricated accordingly.
The following publication, which is the document related to the patent application, is cited herein for reference:    Japanese Patent Application No. 2005-506174
The following publications, which are not related to the patent application, are cited herein for reference:    (1) David, J. T.; “Drop Sizes of Emulsions Related to Turbulent Energy Dissipation Rates”, Chem. Eng. Sci., 40, 839-842 (1985) and David J. T.; “A Physical Interpretation of Drop Sizes in Homogenizers;    (2) Davies, J. T.; “A Physical Interpretation of Drop Sizes in Homogenizers and Agitated Tanks, Including the Dispersion of Viscous Oils”, Chem. Eng. Sci., 42, 1671-1676 (1987);    (3) Calabrese, R. V., M. K. Francis, V. P. Mishra and S. Phongikaroon; “Measurement and Analysis of Drop Size in Batch Rotor-Stator Mixer”, Proc. 10th European Conference on Mixing, pp. 149-156, Delft, the Netherlands (2000);    (4) Calabrese, R. V., M. K. Francis, V. P. Mishra, G. A. Padron and S. Phongikaroon; “Fluid Dynamic and Emulsification in High Shear Mixers”, Proc. 3rd World Congress on Emulsion, pp. 1-10, Lyon, France (2002);    (5) Maa, Y. F., and C. Hsu, and C. Hsu; “Liquid-Liquid Emulsification by Rotor/Stator Homogenization”, J. Controlled. Release, 38, 219-228 (1996); (6) Barailler, F., M. Heniche and P. A. Tanguy; “CFD Analysis of a Rotor-Stator Mixer with Viscous Fluids”, Chem. Eng. Sci., 61, 2888-2894 (2006);    (7) Utomo, A. T., M. Baker and A. W. Pacek; “Flow Pattern, Periodicity and Energy Dissipation in a Batch Rotor-Stator Mixer”, Chem. Eng. Res. Des., 86, 1397-1409 (2008);    (8) Porcelli, J.; “The Science of Rotor-Stator Mixers”, Food Process, 63, 60-66 (2002);    (9) Urban, K.: “Rotor-Stator and Disc System for Emulsification Processes”, Chem. Eng. Technol., 29, 24-31 (2006)